An example of a battery manufacturing method is disclosed in JP 2009-026569 A, in which a sealed-type battery is fabricated in a hermetically sealed container with a leakage testing gas atmosphere. According to the publication, this allows the interior of the battery case to be substantially a leakage testing gas atmosphere, improving the accuracy of hermeticity test for a sealed-type battery.
JP 2010-244898 A discloses the procedure of enclosing battery components, such as a wound assembly and current collectors, into a battery case (i.e., casing), performing a leakage test (hermeticity test), forming a safety vent in a lid, filling an electrolyte solution, and sealing a filling port with a sealing member. Here, the hermeticity test is carried out prior to the step of filling an electrolyte solution. The publication also discloses a technique of leakage test in which helium gas is pumped through the filling port and leakage is checked by determining whether or not the helium gas is detected in the vicinity of the battery case.